Fix unlikely races with GnuTLS, datagrams

Retry some calls if interrupted at inopportune times.
These were found by code inspection.
* src/gnutls.c (gnutls_try_handshake): Simplify by using
new emacs_gnutls_handle_error API.
(emacs_gnutls_write): Remove GNUTLS_E_AGAIN hack since
emacs_gnutls_handle_error now does that.
Use emacs_gnutls_handle_error only on errors.
(emacs_gnutls_read): Retry if gnutls_record_recv returns
GNUTLS_E_INTERRUPTED, to be consistent with emacs_read.
(emacs_gnutls_handle_error): Return 0 on fatal errors,
-1 (setting errno) on ordinary errors, to simplify callers.
Assume that ERR is negative, since it always is now.
Map non-fatal GnuTLS errors to errno values as best we can.
* src/process.c (read_process_output) [DATAGRAM_SOCKETS]:
Retry recvfrom if it is interrupted, to be consistent with
how things are handled when not a datagram channel.
(send_process) [DATAGRAM_SOCEKTS]: If sendto is interrupted,
process pending signals and retry it, to be consistent with
how things are handled when not a datagram channel.

1 files changed, 20 insertions, 8 deletions

diff --git a/src/process.c b/src/process.c
index 06555bac4c0..c0741403b57 100644
--- a/src/process.c
+++ b/src/process.c
@@ -5840,7 +5840,8 @@ read_and_dispose_of_process_output (struct Lisp_Process *p, char *chars,
 
 /* Read pending output from the process channel,
    starting with our buffered-ahead character if we have one.
-   Yield number of decoded characters read.
+   Yield number of decoded characters read,
+   or -1 (setting errno) if there is a read error.
 
    This function reads at most 4096 characters.
    If you want to read all available subprocess output,
@@ -5870,8 +5871,10 @@ read_process_output (Lisp_Object proc, int channel)
   if (DATAGRAM_CHAN_P (channel))
     {
       socklen_t len = datagram_address[channel].len;
-      nbytes = recvfrom (channel, chars + carryover, readmax,
-                         0, datagram_address[channel].sa, &len);
+      do
+        nbytes = recvfrom (channel, chars + carryover, readmax,
+                           0, datagram_address[channel].sa, &len);
+      while (nbytes < 0 && errno == EINTR);
     }
   else
 #endif
@@ -5921,8 +5924,6 @@ read_process_output (Lisp_Object proc, int channel)
 
   p->decoding_carryover = 0;
 
-  /* At this point, NBYTES holds number of bytes just received
-     (including the one in proc_buffered_char[channel]).  */
   if (nbytes <= 0)
     {
       if (nbytes < 0 || coding->mode & CODING_MODE_LAST_BLOCK)
@@ -5930,6 +5931,9 @@ read_process_output (Lisp_Object proc, int channel)
       coding->mode |= CODING_MODE_LAST_BLOCK;
     }
 
+  /* At this point, NBYTES holds number of bytes just received
+     (including the one in proc_buffered_char[channel]).  */
+
   /* Ignore carryover, it's been added by a previous iteration already.  */
   p->nbytes_read += nbytes;
 
@@ -6372,9 +6376,17 @@ send_process (Lisp_Object proc, const char *buf, ptrdiff_t len,
 #ifdef DATAGRAM_SOCKETS
           if (DATAGRAM_CHAN_P (outfd))
             {
-              rv = sendto (outfd, cur_buf, cur_len,
-                           0, datagram_address[outfd].sa,
-                           datagram_address[outfd].len);
+              while (true)
+                {
+                  rv = sendto (outfd, cur_buf, cur_len, 0,
+                               datagram_address[outfd].sa,
+                               datagram_address[outfd].len);
+                  if (! (rv < 0 && errno == EINTR))
+                    break;
+                  if (pending_signals)
+                    process_pending_signals ();
+                }
+
               if (rv >= 0)
                 written = rv;
               else if (errno == EMSGSIZE)